Advances in lightwave technology have made optical fiber a very popular medium for large bandwidth applications. In particular, optical technology is being utilized more and more in broadband systems wherein communications between systems take place on high-speed optical channels. As this trend continues to gain more and more momentum, the need for efficient utilization of the precious real estate on circuit boards, racks/shelves, back planes, distribution cabinets, etc., is becoming ever increasingly important. In order to fulfill expectations across the industry, opto-electronic modules and optic fiber devices need to continue to become miniaturized, thereby taking fill advantage of the maturity of micro- and opto-electronic technologies for generating, transporting, managing and delivering broadband services to the ever increasing bandwidth demands of end users at increasingly lower costs. Thus, the industry has placed an emphasis on small form factor optical connectors, such as the LC connector from Lucent Technologies, Inc. However, miniaturization is tempered by the requirements of transmission efficiency. For instance, with the advent of new standards such as gigabit ethernet, wherein the transmission efficiency is becoming more and more critical, the performance of optical connectors is becoming correspondingly important for healthy operation of the system. Thus, it is desirable to obtain component miniaturization without sacrificing transmission efficiency, and sometimes while improving transmission efficiency.
With the miniaturization of optical modules and optical fiber devices, the management of optical fiber congestion has become an issue at optical interfaces and connection distribution points. One solution is the use of multi-fiber ribbon in which a plurality of optical fibers are organized and molded side by side in a plastic ribbon. It is known to interconnect these ribbon cables by supporting the fibers between two support members made of a monocrystalline material, such as silicon. In the support members are V-grooves formed utilizing photolithographic masking and etching techniques. The fibers are placed side by side in individual V-grooves of one support member and the other mating support member having corresponding V-grooves is placed over the fibers so as to bind or hold the fibers in a high precision, spatial relationship between the mating V-grooves. The top and bottom support members sandwiching the multi-fiber ribbon are typically bonded together with a clamp or adhesive, forming a ferrule of a multi-fiber connector. Two mating ferrules with the same fiber spacing may then be placed in an abutting relationship so that the ends of the fibers of the respective ferrules are substantially co-axially aligned with one another, thereby forming a multi-fiber connection. If desired, such ferrules can be stacked in order to increase the interconnection density.
Multi-fiber ribbons and connectors have numerous applications in optic communication systems. For instance, some opto-electronic and optical application specific integrated circuits (OASIC) devices, e.g, optical switches, optical power splitters/combiners, routers, etc., have several input and/or output ports arranged as linear arrays to which a plurality of fiber are to be coupled. Further, since optical fibers are attached somehow to launch optical signals into these devices and extract optical signals out of these devices, splicing of arrays of fibers (i.e., a multi-fiber ribbon) to such devices can be achieved using multi-fiber connectors. Yet another possible application relates to an optical fan-out fabric where an array of fibers in a multi-fiber ribbon may be broken into simplex or duplex channels for distribution purposes, as is often desired.
A critical factor to the optical efficiency of a multi-fiber ferrule, whether or not stacked, is the alignment of the mating ferrules with regard to one another. To that end, alignment pins are often utilized. Alignment pins are received in alignment pin holes or slots in the respective ferrules so as to hold the ferrules in precise alignment with regard to one another. The alignment pins usually extend parallel to the optical fibers, and are preferably made of a material have a similar coefficient of thermal expansion to the ferrules. In one embodiment, as disclosed in U.S. Pat. No. 4,973,127 to Cannon Jr. et al., alignment pin holes are formed by grooves that are laterally disposed on opposite sides of the optical fiber V-grooves in the support members, such that when two support members are brought together, alignment pin holes are defined by mating alignment grooves. In U.S. Pat. No. 5,620,634 to the present inventor, wherein support members are stacked in order to increase the interconnection density, alignment slots are provided on each row of optical fiber, that is, every support member interface.
A critical factor to the success of any multi-fiber interconnection system is the ease and speed at which it can be assembled. It is desirable that a ferrule stack be assembled relatively quickly with a minimum amount of effort and overhead so that such connection systems can be manufactured economically. Connection systems which call for elaborate and costly procedures for assembly are not likely to be commercially successful because the cost of manufacturing drives up the price above market.
In summary, there continues to be strong market forces driving the miniaturization of fiber optic connection systems, while at the same time demanding that the increasing interconnection density requirements be satisfied. Further, such a connection system should be capable of being manufactured and assembled easily and inexpensively.